DIY LPG conversion on Seat Alhambra

This page is for information on converting a car to run on LPG yourself. I will be convering the conversion of a Seat Alhambra (MPV - same as Ford Galaxy / VW Sharan) to run on LPG. The first pictures are now up and the description is complete, as is the conversion. A few teething problems to overcome and it will be perfect :)

Go to the MPV mailing list link ..

To Begin ..

Take an empty engine bay ..

Have a good look around to see where you can locate the parts required. Click this image to see a larger version. You need to locate a mixer in the intake hose - upstream of the throttle butterfly, a vaporiser somewhere which is fed with coolant water, and any ECUs required. In this case I've found there is room next to the battery tray on the engine side for the vaporiser and on the battery side for the ECUs. The mixer goes in the hose just before the big silver join on top of the engine facing backwards. No catalogue so far lists the Alhambra, but it's a simple case of measuring the external diameter of this housing and finding which general purpose mixer is the right fit (in this case an OML DV115 with a tiny bit taken off the inside with a lathe). Consider your tank options, your kit supplier should be able to advise. In the case of the MPV I've chosen to use a toroidal tank in place of the spare wheel under the rear of the vehicle.

Assemble the kit ..

Talk to a kit supplier, find out what parts you require, get good advice on the options available to you. I have the following -

Start fitting it ..


Location of gas changeover switch and level indicator. Click for larger image, switch is located in previously blank slot (controls rear 1/4 light electric windows on flasher models I think).

Location of vaporiser. There's a bracket going through a slot in the side of the battery tray shroud at the bottom which I cut, this bolts securely to the battery tray and holds the vaporiser in place with it's securing bolt on the back.


The mixer fitted over the throttle body. It is held on with several grub-screws and an airtight seal is made all around it using silicon sealer. The vapour pipe runs directly to the vaporiser (in as straight a line as possible, no more than 30" long with each bend of 6" radius max counting as an additional 6" of pipe - ie 24" with one bend is the maximum recommended). In this picture you can see the stepper motor which will be driven by the feedback controller, the wiring of that comes next.


The injector emulators (on left) and the gas ECU on the right (OMVL Millenium). These are both fairly simple to wire up, the only hard part being identifying the correct wires on the coil, throttle position sensor and lambda probe - especially as there is no manual available for this vehicle yet ! This is no harder than wiring in a car stereo, honestly ..
The engine side of things all finished, standard air-pipe trimmed down slightly and refitted - you can hardly tell I've been in there :)

Pictures for the remainder of this page will follow ASAP

Tank

Now this is a little unusual to say the least. Because of the chosen tank (toroidal to go where the spare wheel is usually fitted under the rear) and the access to this point being only from the underneath I had to actually fit the tank upside down. This only really confuses things because the multivalve for this tank is a 30 degree fixed one for use the other way up. However that's not a big problem because you can fit the multivalve to the tank the other way up and bend the float so that it still reads out properly. Care must be taken when doing this though, as the ullage valve (automatic filler stop) must be activated in the correct place. A few trial fittings and tests by turning the tank over by hand should see it done though.

The sender unit for the tank level gauge is fitted at this stage too, it uses two threaded rods which replace two of the six bolts which hold the multivalve to the tank. These then have a washer and nut on to hold the multivalve down, as well as several other washers and nuts to hold the sensor cap on - this replaces the existing one which should just lever off. The important part of the sensor is the needle which you change for the one currently in the multivalve, which just lifts out. You have to swap the magnet over to the new needle, being careful to get it the same way around else the needle will point the wrong way !

The other thing I fitted at this point was a safety shut-off solenoid, inside the middle of the doughnut tank. I plumbed the output from the multivalve to this solenoid then routed that to the engine bay. This means that the gas is totally shut-off at the tank immediately when the engine stops or in an emergency. Highly recommended. Both this and the level gauge require wiring running to the controller at the front of the car, I ran them both just inside the plastic lip on the inside of the right hand sill.

The tank is held in place with 4 threaded rods, the front 2 come through the floor just near the rear-most seat back mounts and the rear 2 go into the rear cross-member. The left one has to have a hole made above it to get access to the top nuts but the right hand one can just be done by putting a washer and nut onto the rod through an access grommet just next to where the hole goes ! convenient or what :)

Gas lines

I put the filler in the rear RH wing panel, there's a convenient amount of space in the rear locker that side to take the pipe through and down through the floor to the tank. The filler I used came with a very neat little sticker to put on the body and drill through. That was a pretty quick and easy job really.

The main gas feed to the engine bay was quite easy also, there is a natural run once you are over the rear suspension anyway. There are even clips which you can use where the existing petrol lines run, just remember to clip the pipe everywhere that it could possibly move or chafe. The COP11 guidelines specify 600mm which is way too far, I don't think I left more than 300mm between clips - a lot less in some cases. As the exhaust runs all the way down the left side of the vehicle I ran the gas pipe up into the right hand side of the engine bay and then across the top before coming down and forming a loop before going to the solenoid and vaporiser. A relatively straight-forward job if sufficient care is taken.

Electrics

OK, so it's all plumbed in and securely fitted - however it won't work still as there's no signals to the gas ECU. The main inputs it needs are - These are used to decide when to perform certain operations (the main one being switching to/from LPG) and it generates several outputs, the 2 main ones I've used for this vehicle are the lambda emulation signal (to prevent the fuel ECU from complaining) and the changeover signal. The latter is connected to all of the solenoids and the injector emulators such that changeover to LPG can occur when the ECU decides it is ready. This wiring is all fairly straight-forward except for the lambda probe which is difficult to access - however I found that by unplugging the loom side I could feed enough of the wiring through a grommet in the passenger side front floor to tap into the correct wire while the wiring was on the floor. The wiring was then all fed back through the hole and the grommet replaced and sealed.

Now that the wiring is complete I connected a laptop PC to the controller to ensure that all of the signals are correct, and the settings in the controller are OK. Set it to 4 cylinder, select the unusual 5v-0v throttle position sensor range and it was ready to go. I had it inspected by Gas Converters, leak tested, filled with gas and it's away ! 9p a mile here we come :)

Teething

It's been stalling when slowing down if the clutch is dipped at sufficient RPM, just seems to not 'catch' the engine as it slows down. Looking into this ..
Also I've had 2 backfires, and lost power while going along - which I could not explain. One of the pipes I left loose to prevent a backfire damaging the airflow meter had been blown off so the airflow was not providing a reading - however I don't see why that would stop it running on LPG .. my suspicion is that the lambda probe is in need of replacing.
Update - well that wasn't quite true :) I drove the car with the laptop and diagnostic software running on the passenger seat, the mixture was going weak on over-run causing the stalling and blow-backs. I've now set the ECU to open the mixture valve when on over-run and it's much better, though can still stall occassionally. I'll come back to it when the first 1000 miles has been covered and the vaporiser has bedded in some more.

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